Methylene N-heterocycles

N-heterocyclic compounds containing six-membered rings (pyridine and analogues) behave as excellent -acceptors and in turn they provide a rather soft site for metal ion coordination. The 7r-excessive five-membered pyrazole is a poorer 7r-acceptor and a better 7r-donor and it acts as relatively hard donor site. Inclusion of six- and five-membered N-heterocycles like pyridine and pyrazole in one ligand system leads to very attractive coordination chemistry with variations of the electronic properties.555 The insertion of a spacer (e.g., methylene groups) between two heterocycles, which breaks any electronic communication, makes the coordination properties even more manifold. 

Hydrazone Dyes If the diazonium salts of aromatic amines are coupled with the methylene derivatives of N heterocycles, hydrazone dyes (i.e., the monoaza derivatives of the enamine dyes) are obtained. Paper and leather can be dyed in yellow to red shades with these dyes [23], They are moderately lightfast on polyacrylonitrile. If the diazo components contain substituents in the 2-position relative to the amino group that can form a hydrogen bond (e.g., 2-nitroaniline [24] or 1-ami-noanthraquinone [25]), lightfastness is improved considerably (10). 

Ethyl chloroformate/triethylamine Expansion of N,N-heterocycles via bridgehead lactams Elimination of N-methylene bridges... 

Nitrato-N-nitramines. A soln. of startg. aziridine in methylene chloride treated with 1.25 eqs. N2O5 at -10 to —5° for 0.5 to 1 h - product. Y 70%. Reaction is only applicable with strained N-heterocyclics (aziridines, azetidines). F.e.s. P. Golding et al., Tetrahedron Letters 29, 2735-6 (1988). 

A mixture of ethyl chromone-2-carboxylate and 1,2-diaminobenzene heated in a xylene vapour bath to 135 ", the obtained dark melt resolidified after 15 min, and heating continued for another 2 h - 2-(2-hydroxybenzoyl)methylene-3-oxo-l,2,3,4-tetrahydroquinoxaline. Y 44%. F.e.s. D.G. Markees, J. Heterocyc. Chem. 26, 29-32 (1989) review of N-heterocyclics from diamines s. G. Kempter, J. Spindler, Z. Chem. 29, 276-80 (1989). 

Addition of active methylene groups to acetylene-N-heterocyclics <-... 

Acetyleneethers s. Alkoxy-acetylenes, Aryloxy-, Pyrans, tetr ydro-2-acetylene-Acetylene-N-heterocyclics -, addition of methylene groups, active to - 29, 662 Acetyleneketones... 

A mixture of equimolar amounts of homophthalic acid anhydride, veratriylidene-methylamine, and methylene chloride refluxed 10 min., and the resulting soln. allowed to stand 1 hr. at room temp. -> ( )-rran -4-carboxy-3-(3,4-dimethyoxy-phenyl)-2-methyl-3,4-dihydro-l(2H)-isoquinoline. Y 96%. F. e. s. M. A. Haimova et al.. Tetrahedron 33, 331 (1977) N-condensed N-heterocyclics s. M. Cushman, J. Gentry, and F. W. Dekow, J. Org. Chem. 42, 1111 (1977). 

A. Jackowski, S.l. Zones, S.-J. Hwang, A.W. Burton, Diquaternary ammonium compounds in zeolite synthesis cyclic and polycyclic N-heterocycles connected by methylene chains, J. Am. Chem. Soc. 131 (2009) 1092-1100. 

Again, the amide and the N-heterocyclic moiety were placed on different parts of the molecular scaffold, and separated by a methylene bridge (Scheme 10). 

Hou X-F, Wang Y-N, Gottker-Schnetmann I. N-Heterocyclic carbene palladium catalyzed regioselective oxidative trifluoroacetoxylation of unactivated methylene sp C-H bonds in linear alkyl esters. Organometallics. 2011 30 6053-6056. 

The synthesis of bis N-heterocyclic chelate ligand (bNHC) namely l,l -methylene-3,3 -di-2,6-diisopropylphenylimidazole-2,2 -diyli-dene is carried out by modification of the literature procedures (4,5). 

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